An aircraft can include an engine, such as a gas turbine engine, for propulsion of the aircraft. A gas turbine engine can include a fan and a core arranged in flow communication with one another. The core of the gas turbine engine generally includes an air flow path having, in serial air flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section can include one or more compressors used to compress air. The compressed air can be provided to the combustion section where it is mixed with fuel and burned to provide combustion gases. The combustion gases can be used to support operation of the compressor section and the turbine section of the gas turbine engine.
During flight, an aircraft may encounter solid water in the form of ice crystals (e.g., from cirrus clouds) in the flight path of the aircraft. Large amounts of ice water ingested by the aircraft engine can be problematic as energy is expended to convert the water to vapor during the combustion process. This can lead to increased fuel consumption of the engine when solid water in the form of ice crystals is in the flight path of the aircraft.
Variable bleed valves associated with the aircraft engine can be opened in response to the detection of ice crystals. Opening of the variable bleed valves can lead to increased fuel consumption of the aircraft engine. Current methods using estimates of ice content based on one or more temperature sensors can cause the variable bleed valves to open for more time than needed due to uncertainty in the ice content estimate. The impact of opening the variable bleed valves on fuel consumption can be large.